I have the 17-40 f4L, the 24-70 f2.8L and 70-200 f2.8L IS IIUsed on both the 7d and 5d mark II.

Will the 85mm f/1.8 give me noticeably better bokeh or any sharper images because it is a prime lens? I cannot afford another L lens at the moment.

Thanks!

If you have the two 2.8 zooms ...particularly the 70-200 f2.8II ...i'd say the 85mm isn't going to add that much. But if you have extra money to burn and think 1.3 stops will add to your shots...go for it

My main use for my 85mm f/1.8 is the wider aperture for low light use. However, I feel comfortable with using my 5D MK III at ISO 12800 or even 25600 in a pinch, so I'm on the verge of selling it since I picked up a 70-200mm f/2.8 and am planning on a 24-70mmL in the next few months.85mm seems to be a magic spot for lens manufacturers. The sharpest lenses all tend to be 85mm, so from that standpoint, its a good lens to have. But, if you seldom use it, sell it.

I have the same lenses as you and haven't used my 85 f/1.8 very much. The 70-200 is almost always a better choice. Go with a 50mm f/1.4 instead. I have the Sigma and I use that much more often than the 85. You get 1.3 stops more light over the 85 (due to increased aperture and reduced shutter speed). Plus, the depth of field is noticeably different compared to the 2.8 zoom, whereas the depth of field on the 85 is not much different than it is at 2.8.

The 85 f/1.8 is a superlative lens...but I don't think it's going to give you better image quality than your 70-200 II. And the f/2.8 of the 70-200 combined with the high ISO ability of the 5DIII takes care of all reasonable low-light needs.

All that remains is two considerations: shallow depth of field and size.

If you keep the framing the same -- that is, "zoom" with your feet -- then the 70-200 @ 200mm wide open will give you significantly more background isolation than the 85 will. Even at 135mm, the 70-200 should still give you a bit more background isolation.

So, do a quick test: shoot a typical subject framed the way you like it with the 70-200 at 135mm, then zoom it to 85mm, move closer to your subject so you've got the same composition, and compare the two images. If you prefer the perspective of the 85mm shot but wish you had the background separation of the 135mm shot -- or if your typical working distance puts you in the range of the 85mm shot -- then the 85mm is for you. Or, if you wish you had a small and lightweight and unobtrusive lens that can do a bit more than the 70-200 can at 85 mm, then the lens is for you. Otherwise, not.

My guess is that it's probably not worth it for you, but only because you're not complaining about any shortcomings of the 70-200. They're both great lenses....

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The 85mm f/1.8 will give you better images at f/2.8 than the 70-200mm II as well much better light transmission.

In Tstops, the 70-200mm II lens is really T/3.4. It is more than 1/3rd stop slower than f/2.8 (not "huge" in the grand scheme of things, but very real). So the 85mm f/1.8 lens is actually more than twice as bright, about 250% as bright.

The 85mm f/1.8 is also lighter and thus more useful in enabling you to remain fresh and keep getting good photos compared to the 70-200mm lens in real world situations where 85mm is an appropriate focal length and/or when you can zoom with your feet. It is much faster in actual shooting of fast action.

The 70-200 II is what you need when you need a zoom and need that zoom to be as perfect as can be. But an f/2.8 zoom can never compete in situations that a fast, lightweight prime lens is designed for.

The 85mm f/1.8 will give you better images at f/2.8 than the 70-200mm II as well much better light transmission.

Actually, the 70-200 II is sharper at f/2.8 than the 85 f/1.8 at f/2.8, and very significantly so in the corners.

Light transmission is only of a concern for videographers. For still photography, through-the-lens metering takes care of those types of differences. And I really doubt there's much of a T-stop difference between the two when used at the same apertures.

Don't get me worng -- the 85 f/1.8 is a fantastic, great lens. And its usage profile certainly does overlap with the 70-200 II.

It's just that there's only a very, very narrow range of things that the 85 does better than the 70-200, and sharpness emphatically isn't one of them. And, if you've already got the 70-200, there's no point in the 85 unless you actually need one of those very few things (size / weight / noticeability and background separation at that subject distance) that it does better.

My rather non-committal comment earlier was based on the fact you may want to invest in something new based on the way your post was phrased. The 85 f/1.8, if you can find a place for it in your line up, is a great lens.

For portraits you are not going to get the look from 70-200II at 2.8 that you will get from 85 f/1.8 at f2!!! they will look very different. The canon 85 is a dedicated portrait lens... 70-200II, while capable of taking great portraits, is a jack of many trades.

The reason Canon has not updated 85 f/1.8 since 1992 (20 years!), is not because they are lazy, but IMHO because they feel it is still good today, and has relevance.

Also, sharpness is not everything in portraiture, though 85 1.8 is plenty sharp. I will have to give the nod to the zoom on sharpness across the frame though 85 has really good center sharpness which is what you go for in portraiture for the most part.

Importantly, at the same focal length of 85mm, my passing impression was that there was a little more compression with the zoom than with the prime. I haven't tested this very carefully, but you shouldn't expect the same framing or "look" from the two lenses.

I have both the 85 f/1.8 USM and the 70-200 f/2.8L. I find that the 85mm is an excellent portrait lens. It is also small and inconspicuous and focuses really fast. Great lens at a great price. If you can afford it I would buy it.

I will echo RL's comment... 50 f/1.4 is affordable, even slightly cheaper than 85 f/1.8, and will do great portraits...you can walk back a bit and get a wider field of view (35-like "field" not "angle" of view) or closer and get near ~85mm range...

Also you will actually get 2 stops more light from your 2.8 zoom. As for bokeh...it produces lovely blurred background.

The 85mm f/1.8 will give you better images at f/2.8 than the 70-200mm II as well much better light transmission.

Actually, the 70-200 II is sharper at f/2.8 than the 85 f/1.8 at f/2.8, and very significantly so in the corners.

Light transmission is only of a concern for videographers. For still photography, through-the-lens metering takes care of those types of differences. And I really doubt there's much of a T-stop difference between the two when used at the same apertures.

No, the corners wide open on the 85mm f/1.8 are 2,888 line pairs per image height, versus 2,954-3,100 for the 70-200mm II. That difference is almost invisible. At f/2.8 they are essentially the same in resolution figures (28 line pairs difference), but the chromatic aberration of the 70-200 mm II is at least five times worse: 29 - 60% versus only 5% for the 85mm f/1.8.

The shallow depth of field of the 85mm f/1.8 causes halos around out of focus details, making people think that it is not sharp, but for me that's the beauty and my intent in using this lens.

It doesn't impress people watching me take pictures, but my photos impress the people selecting them for running in the news. I can react much more quickly, focus more quickly, and use 3-4 times faster shutter speeds.

There is that much of a Tstop difference when used at the same apertures.

As a reference for those who may own the 50mm f/1.4, the 85mm f/1.8 is much better. Even when stopped down two stops all the way down to f/2.8, the 50mm in the corners is worse than the corners of the 85mm wide open.

helpful how is it that you can use 3-4 times faster shutter speed with an 85mm 1.8 -vs- a 70-200mm 2.8 IS? you can react faster with a prime than a zoom? halos around out of focus objects making things appear less sharp?